Generating a Long-Term Spatiotemporally Continuous Melt Pond Fraction Dataset for Arctic Sea Ice Using an Artificial Neural Network and a Statistical-Based Temporal Filter

The melt pond fraction (MPF) is an important geophysical parameter of climate and the surface energy budget, and many MPF datasets have been generated from satellite observations. However, the reliability of these datasets suffers from short temporal spans and data gaps. To improve the temporal span and spatiotemporal continuity, we generated a long-term spatiotemporally continuous MPF dataset for Arctic sea ice, which is called the Northeast Normal University-melt pond fraction (NENU-MPF), from Moderate Resolution Imaging Spectroradiometer (MODIS) data. First, the non-linear relationship between the MODIS reflectance/geometries and the MPF was constructed using a genetic algorithm optimized back-propagation neural network (GA-BPNN) model. Then, the data gaps were filled and smoothed using a statistical-based temporal filter. The results show that the GA-BPNN model can provide accurate estimations of the MPF (R2 = 0.76, root mean square error (RMSE) = 0.05) and that the data gaps can be efficiently filled by the statistical-based temporal filter (RMSE = 0.047; bias = −0.022). The newly generated NENU-MPF dataset is consistent with the validation data and with published MPF datasets. Moreover, it has a longer temporal span and is much more spatiotemporally continuous; thus, it improves our knowledge of the long-term dynamics of the MPF over Arctic sea ice surfaces

Silver-promoted decarboxylative radical addition/annulation of oxamic acids with <i>gem</i>-difluoroolefins: concise access to CF₂-containing 3,4-dihydroquinolin-2-ones

Described is a silver-promoted decarboxylative radical addition/annulation of oxamic acids with gem-difluoroalkenes enabling the convenient synthesis of various structurally diverse CF2-containing 3,4-dihydroquinolin-2-ones that might find applications in medical chemistry.</p

Helical Airflow Synthesis of Quinoxalines: A Continuous and Efficient Mechanochemical Approach

In this work, we report a novel mechanochemical synthesis method for the synthesis of quinoxaline derivatives&mdash;a spiral gas&ndash;solid two-phase flow approach, which enables the efficient preparation of quinoxaline compounds. Compared to conventional synthetic methods, this approach eliminates the need for heating or solvents while significantly reducing reaction time. The structures of the synthesized compounds were characterized using nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV&ndash;Vis) absorption spectroscopy, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and high-performance liquid chromatography (HPLC). Using the synthesis of 2,3-diphenylquinoxaline (1) as a model reaction, the synthetic process was investigated with UV&ndash;Vis spectroscopy. The results demonstrate that when the total feed amount was 2 g with a carrier gas pressure of 0.8 MPa, the reaction completed within 2 min, achieving a yield of 93%. Furthermore, kinetic analysis of the reaction mechanism was performed by monitoring the UV&ndash;Vis spectra of the products at different time intervals. The results indicate that the synthesis of 1 follows the A4 kinetic model, which describes a two-dimensional diffusion-controlled product growth process following decelerated nucleation

The complete chloroplast genome of Dipterocarpus turbinatus Gaertn. F

Dipterocarpus turbinatus Gaertn. F., naturally distributes in Southern China, which is an elite natural tree with high economic and medicinal value. In study, all chloroplast (cp) genome of Dipterocarpus turbinatus Gaertn. F. was assembled and characterized based on Illumina pair-end sequencing data. The complete chloroplast genome length was 152,279 bp. It contained a large (LSC, 83,862 bp) and a small (SSC, 20,215 bp) single copy region, separated by a pair of inverted repeats of 24,101 bp (IRs). The overall GC content of genome was 37.3%, the corresponding values of LSC, SSC, and IR regions were 35.3, 31.6, and 43.2%, respectively. There were 128 genes in the genome including 84 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. Among all genes, 14 genes contain a single intron and 1 gene has two introns. The result showed that Dipterocarpus turbinatus Gaertn. F. was closely related to Vatica mangachapoi

The complete chloroplast genome of Yunnanopilia longistaminea (Opiliaceae), an endemic species in southwest China

The complete chloroplast genome sequence of Yunnanopilia longistaminea, an endemic species in southwest China, is presented in this study. The total genome size of Y. longistaminea was 148,503 bp in length, with a typical quadripartite structure including a pair of inverted repeat (IRs, 28,075 bp) regions separated by a large single copy (LSC, 84,547bp) region and a small single copy (SSC, 7805 bp) region. The all GC content was 37.3%. The genome contains 117 genes, including 72 protein-coding genes, 37 tRNA genes, and 8 rRNA genes, 13 genes contain a single intron, and 3 genes have two introns. Further, a maximum-likelihood (ML) phylogenetic tree results that Y. longistaminea was closely related to the genera of Champereia manillana